Your entire focus right now should be on getting her through her surgury with understanding and care. While I'm sorry to hear that she needs surgury, it's a great opportunity to shower her with care and attention. Show her you are the man that can take care of her when you are both old, grey and falling apart .
At all costs, avoid any disrespectful statements (like correcting her when you think she's wrong, using sarcasm, bringing up the past, pontificating on any subject etc.). Doing ANY of these things reverses, by a wide margin, any positive things that you do. Think of her heart as a bucket that you are trying to fill with water. Once the bucket is overflowing, she will be in love with you. Each time you speak her LL you will add water. Each time you are disrespectful, or do anything that hurts her feelings, you are drilling holes in the bottom of the bucket. It will never overflow as long as you are putting holes in the bottom.
Your absolute main goal at your stage is to get her to fall in love with you. Forget everything else at this point. Everything will fall easily into place once she's "in love". She will begin to ask for time alone and intimacy from you. Do not, for one second, ask yourself "what is in this for me". You will get a happy marriage at the end of this as long as you stay focused on meeting her needs, which will cause her to fall in love with you.
This can be a difficult stage for very different reasons than when your wife was one foot out the door. Stay patient. Stay loving. Be the man of her dreams. In nobody's dream does the leading man lecture you on what you should be doing, or make you feel ashamed of your past actions. Once she's out of the fog, she will feel bad enough all on her own without your input.
Additionally, I don't know how much time you spend alone with her, having fun, but double or triple that amount of time. Be a joy to date. Plan new adventures and invite her along. Only focus on fun. Show her that a new life together will not be like it was, you will offer more to her than any other man could. Gaze into her eyes and tell her how beautiful she looks under the lights (or candles, or sunset). DO NOT TRY TO MAKE OUT WITH HER, OR ML! Let her decide when the time is right. Instead, put your arm around her, hold her hand, rub her shoulders, run your fingers through her hair. She needs to feel she's with a man that LOVES her, not one that wants to ML with her (that's for later).
Oh, and do the dishes. Pick up after yourself. Ask her "what can I help you with?". Notice when you are out of milk or bread and pick it up on the way home. Dont wait to be asked!! Be a real partner to her. Watch as that "look" comes back into her eyes as she gazes at you!